Gradient nanostructured (GNS) layer was fabricated on the pure titanium using ultrasonic surface rolling process. With the coaction of deformation twinning, phase transformation, and dislocation slip, a spatial gradient of grain size distribution was formed. Nanocrystalline and amorphous phase exist simultaneously on the top surface. The effect of grain refinement, dislocation density, and deformation twinning on strength was analyzed quantitatively. Stress-controlled fatigue tests showed that enhanced fatigue strength was achieved on the GNS Ti due to the synergetic effect of microstructure and unique mechanical properties. The primary mechanism was fatigue-induced grain coarsening sustained the cumulative plastic strain during cyclic deformation and the GNS layer could change the crack initiation mode.

使用超声表面轧制工艺在纯钛上制备了梯度纳米结构（GNS）层。通过变形孪生，相变和位错滑移的共同作用，形成了粒度分布的空间梯度。纳米晶相和非晶相同时存在于顶表面上。定量分析了晶粒细化，位错密度和形变孪晶对强度的影响。应力控制疲劳测试表明，由于微结构的协同作用和独特的机械性能，GNS Ti的疲劳强度得到了提高。其主要机理是疲劳引起的晶粒粗化在循环变形过程中维持累积的塑性应变，而GNS层可以改变裂纹的萌生方式。